The present invention relates to a valve for inflating inner tubes for tyres (alternatively spelled xe2x80x9ctiresxe2x80x9d), to an inner tube provided with said valve and to a wheel for vehicles comprising a tyre mounted on a corresponding rim and provided with said inner tube; more particularly, the invention relates to an inner tube formed by one or more separate compartments and provided with an inflation valve which does not have any fixed systems for connection to the outside of the tyre (alternatively spelled xe2x80x9ctirexe2x80x9d) and the rim.
The wheel is the element forming a link between vehicle and road; it performs the functions of providing the vehicle and its load with a pneumatic-type support system and ensuring, by means of the tyre, a suitable behaviour on the road.
Supporting of the vehicle is provided by the volume of pressurized air contained inside the wheel; for this purpose, the first and the most common of the solutions adopted consists in the use of an inner tube inserted between tyre and rim and inflated with pressurized air introduced into the tube by means of an inflation valve projecting outside the wheel.
More precisely, the wheel comprises a tyre defining a toroidal cavity which is mounted on a corresponding rim and has a bottom surface provided with a central channel and two bead seats on which the beads of the tyre rest in abutment and which are each axially delimited between an end radial surface (projecting shoulder) in an axially external position and an axially internal, annular, raised counter-surface.
The inner tube, inserted between tyre and rim, comprises a torus-shaped expandable tubular body which is generally made of elastomeric material and which can be inflated by means of an associated inflation valve. The valve usually comprises a base for connection to the inner tube and a cylindrical casing (stem) which is fixed to the base and inside which the mechanism for activating the inflating and deflating operations is arranged.
The stem of the valve is usually housed in a suitable hole which is provided on the bottom surface of the rim, more precisely on the channel wall, and from which it emerges into the external environment, at atmospheric pressure, with the corresponding end closed by a cap.
The aforementioned valve allows at least three fundamental operations to be carried out in order to provide the tyre with the correct operating pressure, i.e. inflation and rapid deflation and adjustment to the desired pressure value.
The traditional inner tubes, precisely on account of the fact that they comprise a stem passing through the rim, may pose problemsxe2x80x94which are currently still unsolvedxe2x80x94in some operating conditions of the tyre.
In fact, in conditions of rapid acceleration of the vehicle, it has been noted that the tyre may slip with respect to the rim with a consequent high risk of tearing of the tube at the bottom of the valve or shearing of the valve stem, which results in immediate deflation of the tyre and corresponding loss of stability of the vehicle, with serious risks as regards the safety of the driver and the passengers of the vehicle itself.
The problem is further accentuated in the case of high-performance tyres, but cannot be excluded in other applications, in particular in view of the fact that the present-day vehicles, even though they have a limited power, and hence are incapable of very high speeds, nevertheless allow high driving torques to be transmitted to the ground, so as to give rise to the aforementioned risks.
Essentially the problem of having an inner tube which is safe even in the case of slipping between the tyre and rim is still unsolved.
Moreover, it must be pointed out that the mounting of a traditional inner tube between tyre and rim involves a few problems since the inner tube must be inserted by passing it through the limited space defined between the side of the tyre and rim and then, by means of successive attempts at performing a manual operation which is not particularly easy, introducing the stem of the valve through the appropriate hole on the rim so that it emerges with its end portion into the environment outside the wheel, at atmospheric pressure. In particular, the aforementioned problem arises more frequently in so-called xe2x80x9clow profilexe2x80x9d tyres, where the ratio between the cross-sectional height, measured between the base of the beads and the top of the tread, and the maximum width of the tyre, is equal to or less than 0.7.
The Applicant has realized that there is the possibility of solving the problems according to the state of the art by adopting a flexible container, which may be an inner tube, having the characteristic feature that the valve or the valves necessary for inflating or deflating it do not have any element for connection to the external environment, passing through the rim.
In particular, the Applicant has realized that inflation of the tube could be performed by introducing pressurized air into the space between tyre and rim, so as to deform the tube with respect to its initial shape and thus create a difference in pressure between the internal volume of the tube and the external space and then waiting for the equilibrium between the pressures in the aforementioned environments to be re-established, corresponding to a return of the tube to its original undeformed configuration. Subsequently the air present outside the tube could be left to flow out into the surrounding environment, thus allowing expansion of the tube itself until it completely fills the cavity between tyre and rim.
Advantageously, the initial introduction of pressurized air into the aforementioned space would exert also a thrusting force useful for positioning the beads of the tyre in abutment on the corresponding seats of the rim, against the projecting shoulders, so as to form a preliminary sealed closure of the abovementioned space. According to the Applicant""s idea, the correct and predetermined value of air pressure inside the tube would be reached by allowing the air which has an overpressure with respect to the desired value to flow out by means of a device which has been suitably adjusted to said value.
According to a first aspect thereof, the invention relates to a device for inflating and deflating a flexible container which is elastically expandable for the introduction of pressurized fluid into its internal volume and which can be housed in a cavity which can be isolated from an external environment, at atmospheric pressure, said device being inserted in a wall of said container, characterized in that it does not have elements for connecting the internal volume of said container and said external environment.
More particularly, the container is an inner tube for tyres and the cavity which can be isolated from the external environment includes the toroidal space defined by a tyre mounted on the corresponding mounting rim.
In a first embodiment thereof, the device according to the invention comprises three separate valves for separately performing the three operations fundamental for operation of the -tube, i.e. at least one first inlet valve for inflating the tube with pressurized fluid, at least one second adjustment valve for regulating and maintaining the pressure existing inside the tube within a predetermined range of values, and at least one third discharge valve for rapid deflation of the tube.
In a second embodiment of the device a single valve performs the two functions of adjustment and rapid deflation of the tube, the inflating function being assigned to a second valve.
In another preferred embodiment of the invention a single device performs all three required functions, i.e. it combines an inflation valve with a second valve for adjustment and rapid deflation of the tube.
In all the cited embodiments the function of rapid deflation of the tube may be advantageously performed by acting, from the outside, on the mechanism activating the valve so as to cause opening thereof, for example by means of remote interaction based on the creation of electric or electromagnetic fields or by means of remote commands with specific operating frequencies or with direct mechanical actions on said activation mechanism performed using instruments passing through the rim after having opened in the wall thereof special openings provided specifically for this purpose.
Depending on the selected type of inflation valve, closing of said valve may be effected by means of an overpressure of the inflating fluid or by means of a mechanical effect as a result of interference between the valve body and an opposition surface.
It is pointed out here that the term xe2x80x9cpressurexe2x80x9d, unless otherwise specified, is always understood as being an overpressure with respect to atmospheric pressure. In a preferred embodiment thereof, the device comprises a single rigid body incorporating an inflation valve, an adjustment valve and a deflation valve; even more preferably the three aforementioned valves are incorporated in a single actuating mechanism.
According to a second aspect thereof, the invention relates to an inner tube for vehicle wheel tyres which is elastically expandable by introduction of pressurized fluid into its internal volume and is provided with a device for the introduction and extraction of said fluid respectively into and from said volume, said device being inserted in a wall of the inner tube. The inner tube can be housed in the cavity which is defined by the tyre mounted on its operating rim, isolated from the external environment at atmospheric pressure. The inner tube is characterized in that its inflation device does not have elements for connecting the internal volume of the tube and said external environment.
In a preferred embodiment the inner tube is moulded and vulcanized in a toroidal shape so that the elastic reaction determined by a deformation imparted to said tube tends to cause it to return into its original shape.
According to a third aspect thereof, the invention relates to a tyre wheel for vehicles, comprising a tyre mounted on the corresponding mounting rim, said tyre mounted on said rim defining a toroidal cavity which can be isolated from the external environment at atmospheric pressure, and an inner tube inserted inside said cavity and provided with an inflation device, characterized in that said device does not have any system for connection to said rim, designed to fix the circumferential position of said tube with respect to the rim.
According to a fourth aspect thereof, the invention relates to a tyre comprising a pair of axially facing sidewalls which terminate in a pair of beads for assembly of the tyre on a corresponding mounting rim and which define a first toroidal cavity closed by an elastically deformable circumferential baffle which is fixed to the said sidewalls and in which a device for inflation and deflation of the tyre is inserted. When the tyre is mounted on the rim, a second toroidal cavity is defined between the baffle and the rim and both the aforementioned toroidal cavities can be isolated from the external environment at atmospheric pressure.
The tyre according to the invention is characterized in that said inflation and deflation device does not have elements for connecting the inside of the first cavity and the aforementioned external environment at atmospheric pressure.
In a particular embodiment of the invention, this baffle is formed by a circumferential portion of the casing of an inner tube which is elastically expandable and the remaining part of which casing adherent to the internal surface of the tyre, preferably by means of vulcanization.
The aforementioned inflation and deflation device, which does not have elements for connecting the inside of the inner tube and the environment outside the wheel at atmospheric pressure, is inserted in the free wall portion of the inner tube.
According to a fifth aspect thereof, the invention relates to a method for inflating and deflating an inner tube inserted in the toroidal cavity, isolated from the external environment, defined by a tyre mounted on the associated rim, and for controlling the value of the pressure inside the tube, said inner tube being provided with an inflation and deflation device which does not have any element for connection to said external environment at atmospheric pressure, designed to fix the circumferential position of said tube with respect to said rim.
The aforementioned method comprises the following steps:
a) introducing pressurized air into said toroidal cavity until a predetermined pressure value is reached such as to cause contraction of the volume of the tube and a consequent elastic reaction of the materials which form said tube and are deformed by said contraction in volume;
b) waiting for the pressure inside the inner tube, as a result of said elastic reaction of the tube, to return to equilibrium with the air pressure outside said tube, in the space defined between tyre and rim;
c) discharging the pressurized air remaining in said space between tyre and rim;
d) waiting for the inner tube to have completed its expansion until it comes into contact with the rim and tyre;
e) isolating said space between tyre and rim from the external environment at atmospheric pressure.
In a first embodiment, the method makes use of a device provided with an air inlet valve of the xe2x80x9cnon-returnxe2x80x9d type and comprises the step of causing closing of said valve owing to the positive difference in pressure between the inside and outside of the inner tube, at the start of the step c).
In a second embodiment, the method makes use of a device provided with an air inlet valve of the xe2x80x9cnormally openxe2x80x9d type and comprises the step of causing closing of said valve as a result of interference between the device and an opposition surface, in particular as a result of contact between the inner tube and the wall of the rim. This method requires that discharging of the air during the step c) should be performed very rapidly, i.e. such that the pressurized air contained inside the tube causes almost immediate expansion of said tube, resulting in closing of said valve as a result of contact with the wall of the rim before a significant quantity of air has time to escape through the aperture of the inlet valve, which is open towards the outside.
In a different embodiment, the method also makes use of a device provided with a adjustment valve of the xe2x80x9cnormally closedxe2x80x9d type, in which an obturator keeps the valve closed as a result of an elastic-type thrusting force with a predetermined value and opens the latter under the effect of a thrusting force in the opposite direction having a value greater than the predetermined value.
In a further embodiment the method makes use of a device provided with a discharge valve of the xe2x80x9cnormally closedxe2x80x9d type in which an obturator keeps the valve always closed until a deliberately performed action causes opening thereof.